In general, asbestos is excellent in sound-absorbing properties, thermal insulation properties, corrosion resistance, and chemical resistance, and is cheap. For this reason, asbestos has been widely used as construction materials, fireproofing materials, refractory materials, insulation materials, thermal insulating materials, electrical insulating materials, materials for electrolyte membrane, and materials for brake lining. Nevertheless, it has been reported since 1970s that asbestos has an adverse effect on human beings. The fibres in asbestos are made up of needle-like crystals having a diameter of from 0.02 μm to 0.2 μm. Thus, asbestos was known as a highly carcinogenic substance, that is, if the fibres in asbestos are inhaled into the respiratory system, they remain in it for a long period of time, so that lung cancer, coniosis, or malignant mesothelioma in which cancer occurs at a pleura site is caused via the latent period of 20 to 40 years. Thus, International Agency for Research on Cancer (IARC) under World Health Organization (WHO) designated asbestos as a first-class carcinogenic substance, and particularly also designated talc contained in asbestos as a first-class carcinogenic substance, leading to an increase in the seriousness of a problem.
In recent years, as consciousness of environment conservation grows increasingly, there is a demand for a method for stably treating asbestos waste generated during the dismantling of a building. In general, conventionally, for the sake of the treatment of asbestos waste generated, the waste is melted at a high temperature of more than 1500° C. or is reclaimed in a treatment facility. However, the former method entails a problem in that the cost is high due to the use of a large amount of power and fossil fuel energy, there may remain a certain amount of asbestos component after its treatment, and an environmental pollution may be caused. In addition, the latter method also entails a problem in that it is difficult to secure a waste reclamation site, and asbestos contained in the asbestos waste is not treated by chemical modification, and thus a possibility of leakage of asbestos cannot be excluded due to negligent management and inadvertent accident.
Accordingly, there has been proposed Korean Patent Laid-Open Publication No. 2002-0032672 disclosing an asbestos waste treatment method in which asbestos waste is introduced into an opened container, which is in turn covered by a lid for storage and recovery, and then is charged together with a steelmaking raw material such as scrap into an electrical furnace for steelmaking so that the opened container itself is melted. This method has an advantage in that handling of the opened container is easy and the treatment time and cost can be suppressed, but does not suggest or teach a method for recycling the waste. Meanwhile, there has been proposed Korean Patent Registration No. 10-0891372 disclosing a method of preparing a thermal insulating material using waste asbestos, which comprises the steps: dissolving a decomposed products of waste asbestos in a solution containing at least one selected from the group consisting of sulfuric acid, hydrochloric acid, hydrofluoric acid, and nitric acid to prepare a waste asbestos-containing solution in a sol state; neutralizing the waste asbestos-containing solution with an alkaline solution containing at least one selected from the group consisting of sodium hydroxide, potassium hydroxide, lithium hydroxide, and cesium hydroxide to obtain a neutralized waste asbestos-containing solution; and mixing the neutralized waste asbestos-containing solution with at least one selected from the group consisting of a magnesium compound, a silicate compound, and a silicic acid solution compound to prepare a solid compound in a gel state. This method has an advantage in that the waste asbestos can be recycled as an environmentally friendly material while maintaining thermal insulation properties and non-flammable properties, but has a drawback in that a number of dangerous reagents are used, the treatment method of the waste asbestos is complicated, and its application is limited to the thermal insulating material. In addition, Japanese Patent Laid-Open Publication No. Hei 2002-173358 discloses a method of manufacturing a porous ceramic material having water permeability using asbestos waste and sewage sludge. This method has advantage in that waste treatment cost is saved, but the application of the resulting ceramic material is disadvantageously limited to blocks due to the physical properties such as excellent flexural bending strength.
Accordingly, the present inventors have made extensive efforts to solve the above-described problems occurring in the prior art and, as a result, have found that a lightweight construction material having excellent physical properties can be manufactured without detection of any asbestos components by adding silicon carbide, loess, zeolite, and half silty clay to asbestos waste, thereby completing the present invention.